To fulfill the research goal of deriving high energy and high specific power in a sustainable, safe, and cost-effective manner, Prussian Blue Analogue (PBA)-based Na⁺ ion hybrid capacitors have drawn great interest. However, inherent poor conductivity and metal dissolution problems limit their full-scale exploration as a cathode material. This work attempts to address the above two challenges by compositing a Fe-PBA (Na_xFe[Fe(CN)₆]·nH₂O) (FPBA) with reduced graphene oxide (rGO). The highly conductive nature of rGO boosts the overall conductivity of the FPBA/rGO composite, rendering improved rate performance. At the same time, the surface and edge functional groups (epoxy, hydroxy and carboxylate) on rGO provide firm anchorage to surface Fe ions of FPBA through coordination and thus suppress the metal dissolution, eventually leading to longer cyclability. Due to the synergistic effect of rGO and FPBA, the FPBA/rGO composite also shows significantly enhanced charge storage capacity (437 C g⁻¹ at 1 A g⁻¹) compared to FPBA (204 C g⁻¹ at 1 A g⁻¹). The detailed mechanistic and kinetic studies reveal that, besides faradaic-type charge storage, FPBA/rGO also involves a significant portion of electrical double layer charging due to the presence of rGO. The hybrid charge storage mechanism in FPBA/rGO enables the fabricated symmetric supercapacitor device (FPBA/rGO//FPBA/rGO) to exhibit high specific energy as well as specific power (^maxE = 62.32 W h kg⁻¹ @ 0.9 kW kg⁻¹; ^maxP = 9.0 kW kg⁻¹ @ 31.92 W h kg⁻¹). Moreover, owing to suppressed metal dissolution, the symmetrical device having the FPBA/rGO composite electrodes shows excellent capacitive retention of 91% after 10 000 cycles compared to that with the FPBA-based device (75%).

中文翻译：

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通过将 FePBA 锚定在 rGO 上，通过减少金属溶解和提高电导率来提高钠离子水基超电容的循环稳定性和速率性能


为了实现以可持续、安全和具有成本效益的方式获得高能量和高比功率的研究目标，基于 Prussian Blue Analogues （PBA） 的 Na+ 离子混合电容器引起了极大的兴趣。然而，固有的低导电性和金属溶解问题限制了它们作为正极材料的全面探索。这项工作试图通过将 Fe-PBA （NaxFe[Fe（CN）6].nH2O） （FPBA） 与还原氧化石墨烯 （rGO） 合成来解决上述两个挑战。rGO 的高导电性提高了 FPBA/rGO 复合材料的整体导电性，从而提高了倍率性能。同时，rGO 上的表面和边缘官能团（环氧树脂、羟基和羧酸盐）通过配位为 FPBA 表面的 Fe 离子提供牢固的锚定，从而抑制金属溶解，最终导致更长的循环性。由于 rGO 和 FPBA 的协同作用，与 FPBA（1 A g-1 时 204 C g-1）相比，FPBA/rGO 复合材料也显示出显着增强的电荷存储容量（1 A g-1 时为 437 C g-1）。详细的机理和动力学研究表明，除了法拉第型电荷存储外，由于 rGO 的存在，FPBA/rGO 还涉及很大一部分双电层电荷。FPBA/rGO 中的混合电荷存储机制使制造的混合对称超级电容器器件 （FPBA/rGO//FPBA/rGO） 能够表现出高比能量和比功率（最大 E = 62.32 Wh kg-1 @0.9 kW kg-1;最大 P = 9.0 kW kg-1 @ 31.92 Wh kg-1）。此外，由于抑制了金属溶解，与基于 FPBA 的器件 （75%） 相比，具有 FPBA/rGO 复合电极的对称器件在 10000 次循环后显示出 91% 的优异电容保持率。